The invention relates to an amorphous low-retentivity alloy, which contains cobalt, manganese, silicon and boron.
As is known, an amorphous metal alloy can be manufactured in a process of cooling a corresponding melt so quickly that it solidifies without any crystallization occurring. Thus the amorphous alloys can be obtained immediately upon casting thin bands whose thickness, for example, amounts to a few hundredths mm and whose width can amount to a few mm through several cm.
The amorphous alloys can be distinguished from crystalline alloys by means of x-ray diffraction methods. In contrast to crystalline alloys or materials, which exhibit characteristic sharp diffraction lines, the x-ray diffraction picture of an amorphous metal alloys has an intensity, which changes only slowly with the diffraction angle, and is similar to the diffraction picture for fluids or common glass.
Depending on the manufacturing conditions, the amorphous alloys can be entirely amorphous or comprise a two-phase mixture of both the amorphous and the crystalline state. In general, what is meant by an amorphous metal alloy is an alloy which is at least 50%, preferably at least 80% amorphous.
There is a characteristic temperature, the so-called crystallization temperature, for every amphorous metal alloy. If one heats the amorphous alloy to or above this temperature, then it is transformed into the crystalline state in which it remains after cooling. However during thermal treatments below the crystallization temperature, the amorphous state is retained.
Known low-retentivity amorphous alloys have a composition corresponding to the general formula M.sub.100-t X.sub.t, whereby M signifies at least one of the metal elements Co, Ni and Fe; and X signifies at least one of the so-called vitrifying elements B, Si, C and P; and t lies between approximately 5 and 40. Further, it is known that such amorphous alloys, in addition to the metal elements M, can also contain additional metal elements, such as the transition metal elements Cr, Mo, W, V, Nb, Ta, Ti, Zr, Hf and Mn and that, in addition to the vitrifying elements or, under certain conditions, even instead of these elements, the elements Al, Ga, In, Ge, Sn, Pb, As, Sb, Bi or Be, can also be present (see German OS 2,364,131; German OS 2,553,003; German OS 2,605,615; Japanese OS 51-73923).
Of particular interest among the amorphous low-retentivity alloys are those alloys which have a small magnetostriction, which is as disappearingly small as possible. The smallest possible saturation magnetostriction .lambda..sub.x, is a significant pre-condition for good low-retentivity properties, i.e., a low coercivity and a high permeability. In addition, the magnetic properties of amorphous alloys, which have disappearingly small magnetostriction, are practically insensitive to deformations, so that these alloys can be easily wound into cores or can be processed into shapable screens, for example, fabrics of interlaced ribbons. Further, alloys with a zero magnetostriction are not induced into oscillations under alternating current operating conditions, so that no energy will be lost to mechanical oscillations. The core losses can therefore be kept very low. Moreover, the disruptive hum, which frequently occurs in electro-magnetic devices, is also eliminated.
Within the above mentioned general composition range of low-retentivity amorphous alloys, there are known groups of alloys with particularly low magnetostriction. A group of these alloys has the composition (Co.sub.a Fe.sub.b T.sub.c).sub.y X.sub.1-y, wherein T signifies at least one of the elements Ni, Cr, Mn, V, Ti, Mo, W, Nb, Zr, Pd, Pt, Cu, Ag and Au and X signifies at least one of the elements P, Si, B, C, As, Ge, Al, Ga, In, Sb, Bi and Sn. In addition, the following conditions are present: y is in a range of 0.7-0.9; a is in a range of 0.7-0.97; b is in the range of 0.03-0.25, and a+b+c=1 (see German O.S. 2,546,676).
Another known group of amorphous alloys with magnetostriction values between approximately +5.multidot.10.sup.-6 through -5.multidot.10.sup.-6 has a composition corresponding to the general formula (Co.sub.x Fe.sub.1-x).sub.a B.sub.b C.sub.c, wherein x lies in the range of approximately 0.84 through 1.0; a lies in the range from approximately 78 through 85 atomic %; b lies in the range from approximately 10 through 22 atomic %; c lies in the range from 0 through approximately 12 atomic %; and b+c lie in the range from approximately 15 through 22 atomic %. In addition, these alloys, with reference to the overall composition, can also contain up to approximately 4 atomic % of at least one other transition metal element such as Ti, W, Mo, Cr, Mn, Ni and Cu and up to approximately 6 atomic % of at least one other metalloid element such as Si, Al and P, without the desired magnetic properties being significantly diminished (see German 0. S. 2,708,151).
Low saturation magnetostrictions are found in amorphous alloys, which essentially consist of approximately 13 through 73 atomic % Co, approximately 5 through 50 atomic Ni, and approximately 2 through 17 atomic % Fe, wherein the total amount of Co, Ni and Fe is approximately 80 atomic %, and the remainder of the alloy essentially consists of B and slight contaminations. These alloys, with reference to the overall composition, can likewise contain up to approximately 4 atomic % of at least one of the elements Ti, W, Mo, Cr, Mn or Cu and up to approximately 6 atomic % of at least one of the elements Si, Al, C and P (see German 0.S. 2,835,389).
Finally, another known group of amorphous alloys with low saturation magnetostriction has the corresponding formula (Fe.sub.a Co.sub.b Ni.sub.c).sub.x (Si.sub.e B.sub.f P.sub.g C.sub.h)y, wherein a, b, c, e, f, g and h, respectively signify the mol fractions of the corresponding elements and a+b+c=1 and e+f+g+h=1 and x or, respectively, y signifies the overall amount in atomic % of the elements within the appertaining parentheses with x+y=100, and the following relationships are valid: 0.03.ltoreq.a 0.12; 0.40.ltoreq.b.ltoreq.0.85; 0.ltoreq.ey.ltoreq.25; 0 .ltoreq.fy.ltoreq.30, 0.ltoreq.g+h.ltoreq.0.8 (e+f) o.ltoreq.e,f,g,h.ltoreq.7 and, preferably, 20.ltoreq.y.ltoreq.35. Further, these alloys, with reference to their overall composition, can additionally contain 0.5 through 6 atomic % of at least one of the elements Ti, Zr, V, Nb, Ta, Cr, Mo, W, Zn, Al, Ga, In, Ge, Sn, Pb, As, Sb and Bi (see German 0.S. 2,806,052).